Radiation detection portals and stations are used, for example, to monitor vehicles at international border crossings, to monitor shipments at seaports, and to monitor people, luggage, and cargo at airports in order to detect and prevent the movement of potentially dangerous radiation emitting devices and materials. These radiation detection portals typically use various combinations of radiation detectors to detect and identify gamma and neutron radiation. A specific problem with these measurements results often occurs when the vehicle or other object being measured for radiation does not pass through the portal in a continuous manner, but rather stops within the portal because of traffic or other reasons. Such intermittent motion may adversely affect the accurate interpretation of radiation measurements. What are needed therefore are improved systems and methods for interpreting radiation measurements from radiation monitoring portals through which vehicles, cargo, or persons pass, or for monitoring radiation where vehicles, cargo, or persons may intermittently stop while passing through the portal or station.